Welding apparatus



` April 13 1937- H. A. w. KLINKHAMER Er AL 2,077,114

WELDING APPARATUS Filed March 4, 1936 5 Sheets-Sheet 1 April 13 1937. IH. A. w. KLINKHAMER Er AL 2,077,114

WELDING APPARATUS Filed March 4, 1936 5 Sheets-Sheet 2 /9 fr0/PAMI vApril 13, 1937. H. A. w. KLxNKHAMER Er AL 2,077,114

WELDING APPARATUS o Filed March 4, 1956 3 Sheets-Sheet 3 Patented Apr.13, i937- umrro s'rirrrsl rAj'rl-ziw'r\` oFF-lcs Hendrik Abraham.Wijnand Klinkhamer, Clamor August Lamberts; f Voorhoeve,

hoven, Netherlands,

Nicolaas Anthony Johannes and Frans Hendrik de Jong, Eindassignors to N.V. Philips Gloeilampenfabrieken, Eindhoven, Netherlands ,y

Application March 4, 1936, Serial No.

` In the Netherlands March 13, 1935 .e claims. t (ci. r11-119) I D. C.welding, the three-phase supply current is Our invention relates towelding apparatus in vvwhich one or more rectifyingtubes are used toproduce D. C. welding current Lfrom an A. C. supply, and Vmoreparticularly to welding appa- .ratls for welding. with both A. C. and D.C. curlen l rotating machinery,` such as generators, such a D. C.welding apparatus has a low initial cost,

isvery easy to operate, andzhas particular advantages when used forwelding smallwork-pieces.

.. a welding apparatus However, an apparatus of the above type designedVfor small weldingvcunents, can not be used for large welding currents'due to the small ovr- 20 load capacity of the reetifying tubes. On theother hand, if the apparatus is designed for large welding currents,this involves not only a higher initial cost, but also a low eillciencywhen 1 using the apparatus rent in an eiici'ent and Veil'ective manneras rel gards the load on the transformer and on the supply mains.

' A`further`cbject of our which may be eii'iciently used on twodiii'erent supply voltages.

According to our invention. the transformer is built up of a pluralityof single-phase trans-` former portions. and switching means areprovided for changing-over from D. C. to A. C.`weld4 ing whereby thelprimary as well as the secon windings or parts thereof are connected inpar.- allel. and whereby the transformer is connected in single-phaseandthe A. C. welding current is taken directly from the secondary windings.`A very simple circuit arrangement. which is ""highlyconoinical asmaterial, Ais obtained former from two tions and by so by bimdinglupjtnetramknown devices have the disinvention is to provide.

regards the utiiimtion oi' single-phase transformer porconnecting thewindings in A l supplies A. C. weldirg current. e. l

'I'he welding apparatus according to the inven' f com-panying drawings,in which:

transformed into symmetrical four-phase current by the use of thewell-known Scott connection. It is generally desirable to provide uponthe transformer one or more auxiliary windings and connect thesewindings in series with one of the other transformer windings when theapparatus tion' is universal and gives voptimum results when used'foreitherv A. C. or D. 'C. welding. With D. C. welding, small work-pieces,such as thin l sheets, can be welded with all the inherent advantageso'f D.C. welding. On the other hand,

during A. C. welding, the welding curi-ent is taken directly from thetransformer windings in which case 1the transformer may be overloadedwithout damage, particularly for the short periods .occurring inwelding. Thiatogether with the parallel connection of a number ofwindings, makes the apparatus particularly adapted for the A. C. weldingof the larger work-pieces requiring a comparatively high current. Asduring A. C. welding the rectifying tubes are not in operation theirlife merely depends upon their use in D. C. welding, which is such asnot to require their overloading, and which makes their replacement lessfrequent.

\ In order that our invention may be clearly understood and readilycarried into eilect it will be more fully described with reference vto'the ac- Figure 1 is a schematic diagram of al welding apparatusaccording to the invention; Fig. 2 is a schematic diagramcfa weldingapparatus according to another embodiment oi' the invention; d

Figs. 3 and 4 are diagrams illustrating the connections of the primarywindings of Fig. 2 for D.` C. welding at diiierent supply voltages.

Figs. 5 and 6 are diagrams showing the connections oi' the primarywindings of the transinsign.

jformer of Fig. 2 for A. Ce welding at diii'erent supply voltages.

Fig. 7 is a'K apparatus according tostill another embodiment of theinvention; 1 Fig."8 is a schematic diagram ci amusement for connectingthe primaryl windings of Fig. 7 to the supplymains. l

9 isa side view ot a plug-type connector suitable for use in the weldingapparatus shown Figure 1 showsva welding, apparatus which supplieseither D.'C. or

scliematicdiagram of a welding s' switching' A.- C. jwelding current l20transformer portion are from an AI C. supply connected to terminals U,V, and W, and comprises a transformer 50, two switches 4 and 5, twofull-wave rectifying tubes I and 2, together with a welding electrode 1,and 5 a work-pie 0. The transformer 50 consists of two single-l phasetransformer portions O and P whosecores have a common yoke E. Providedon the transformer portion O are ltwo primary windings S1 and Szinterconnected at ||5, and a secondary winding Se having a central tap'|0|. The transformer portion P is provided with primary windings S and Sinterconnected at ||5, and a secondary winding S1 having a central tap|02. l5 Arranged on the cores of transformer portions O and P so as tobe tightly coupled with the primary windings thereof, are two auxiliarywindings Sa and So.-

The primary and secondary windings of each disposed on differentportions or legs of the core in order to increase the leakage,A however,the same eilect may be obtained by using, between the primary andsecondary windings, adjustable iron bridge pieces (not shown). Theprimary windings S, .S1 and S1 are connected in accordance with theScott arrangement. I

The switches 4 and 5 are of the multipole double-throw type, and when intheir left-hand position, as shown, make the required connections for-supplying a D. C. welding current, whereas in theirright-hand positionmake the connections for A. C. welding. The switches 4 and 5 arepreferably interlocked so that .they will both be 1n their rightorleft-hand positions.

Switch 4 comprises a member 14 upon which are mounted insulated fromeach other four contact arms 6|, 52, 63, and 54 having heel points |03,|04, |05, and |05 respectively. In the left- 4,0 hand position of theswitch, as shown, the arms 6|, 52, 53, and 54 contact with contacts |01,|00-, and ||3 respectively, whereas inl the right- I hand position theycontact with contacts |00, 0, ||2 and ||4 respectively, The heel point|03 is connected to the point ||5 between windings S1 and S2, heel point|05 is connected to the point l0 between windings S and S15, whereasheel points |04 and |05 are connected to the free ends of 50 windingsSand S15. Contact |01 is permanently connected through conductor ||1 tocontact point |09, contact ||0 is connected through conductor v| I0 tothe terminal U and to the free end of winding S1, contact is connectedto ter- 5 'minal W, contact ||4 is connected through a conductor ||0 tothe terminal V and to the free end of windingsSz. Contacts |00, ||2, and||,3 are not used. f i

Switch 5 is similar to switch 4 and has six o arms 05,66, 61, 68, 69 and10, which in the lefthand position of the switch contact with contacts.|I9, |21, |23, |25, |21` and |20 respectively, `whereas in theright-hand position of the switch they contact with contacts |20, |22,|24, |20, |28, and |30 respectively. The heel points of arms 65 and 55are connected to the ends offsecondary winding S5, and the heel pointsof arms 01 and-f 08 are connected to the ends of secondary winding S1.Contact points ||0 and |2| 70 are connected respectively to the rtwoanodes of tube whereas' contacts |23 and |25 are connected respectivelyto the anodes of Ftube 2.

Contact point |22 is connected through a conductor |3| to one end ofwinding Se, whose other end 75 is connected through conductor |32, at 11to heel f arms 55, $5, 51, and4 60 ever, as in many tracts |22 and |20respectively,

nected through switch arm of arm 10,' and through conductor 10 tocontact point |20.

The conductor |3| is connected at point 10 to a conductor 0| connectingcontact point |20 to one end of winding Se whose other end is connectedthrough conductor 00 to the heel point of arm 00. The contact points|20, |24, |21, and |20 are not used.

The electrode 1 is connected through a conductor 15 to the taps|0| and|02 of the secondary windings Se and S1, whereasthe work-piece 0 isconnected through a conductor 10 to the conondary windings of heatingtransformers 1| and 12, which supply heating current to the cathodes ofthe tubes and 2. The transformers 1I and 12 have their primary windingsconnected in series through a switch 13 to a suitable alternatingcurrent supply.

Instead of using separate heating transformers, the cathode heatingcurrent maybe provided from windings located on the core of thetransformer 00. Furthermore, the connections of the electrode 1 andwork-piece 0 may be reversed. 1

With switches 4 and 5 in their left-hand position, as shown, theapparatus supplies D. C. welding current. Winding S has one endconnected through contact arm 02, conductor ||1, and arm 5| to point||5, whereas the free ends of windings S1, Si, and S are connected tothe terminals U, V and W respectively. Windings S5, Se and S15 are notin use in D. C. welding.

.Switch 5 being 'in its left-hand position the anodes of tubes and tothe ends of `windings Se and S1, and the D. C. welding current issupplied through conductors 15 and 10.

To place the apparatus in condition for A. C. welding, switches 4 and 5are moved into their right-hand position, With switch 4 in its righthandposition, windings S1 and Si are connected in series across theterminals a circuit including terminal U, conductor ||0, windings S1 andS1 and conductor ||9 to terminal V. Coils S and S15 are ries acrossterminals U--V through a circuit including terminal U, arm 62, coils Sand S15, arm 54 and conductor ||0 to terminal V. The winding S15 isgiven the proper number of turns whereby equalvoltages are induced inthe two parallel groups consisting of windings S1 and Sz, and of S andS15.

'Ihe secondary windings may be connected in parallel in various ways forA. C. welding; howtypes o'f'fwelding the voltageloss of the transformermay be too high, we reduce this by connecting the windings S5 and So in'parallel with each other and in series with the parallel connection ofthe right-hand portion of windings Se and S1. More particularly, withswitch 5 in its right-hand position, the right-hand ends of windings S5and S1 are connected throughswitch arms 50 and 00 andcontothe conductor|3|. The circuit then passes through two parallel circuits includingwindings Sa and Se respectively. One of these parallel circuits ma! betraced from conductor. Sa, conductor |32 to point 11, whereas the otherparallel circuit may be traced from point 10 on conductor |3|, throughconductor 0|, winding Se conductor 00, switch arm .00, contact |20, and

conductor 19 to point 11. The point 11 is con- 10, contact |30 and 2 areconnected throughr also placed in se- |3| through winding tact point |30and to the midpoints of the sec- Y U-V through described in connectionwith the terminals U and `nur:menu sgarenile `tweenthetel'lliinalsconductor 'I6 l rangement prises a transformer 60' adapted to beconnected to a three-phase supply and consisting oi' two single-phasetransformer portions O and P' having a common yoke. The windings of thetransformer portions O and P may be connected in accordance withtheScott connection so that a four-phase secondary voltage is obtained.

In order that the transformer can he used with two different supplyvoltages the trans# former portion O' is provided with two primarywindings Si and S2 and a secondary winding Se, whereas portion P' is.provided with three primary windings S3, S4, and. S land a secondaryWinding Si. A terminal block 6 is provided for making thev necessaryconnections between the primary windings for, diierent supply voltages.For this'purpose the block 6 is provided with six terminals U, V, W, X,Y- and Z; the terminais U, V and W beingconnected to a suitable supplyof three-phase voltage, and the terminals X, Y-and Z a switching device4.

The switchl is similar in design and function to the switch 4 oi'Fig.'1, .and in its righthand position, asfshown, makes thenecessaryprimary connections stor D. C. welding, whereas inl itsleft-hand positionjmakes the necessary primary connections for A. C.welding The secondary connections are similar to those Fig.V 1; a switchl-'similarto switch 5 in Fig, 1'-in its-leftwinding's Se and S7. whichwere 90 out of phase during the D. C. welding, wi1l'be in phase dur ingthe A. C. welding. As windings Se and Si have the same number of turns.equal voltages are induced therein and they can be connected in parallelbetween A. C. welding terminals |35 and |36 by means of the switch 5.lThis arhas the advantage that all the windings are utilized during A. C.welding, and thus the copper of the transformer is utilized as eco-.-nomically as possible."

As the lsecondary alternating Avoltage will not be exactly equal to thatvin the case of D. C. op-

-eration, the primary windings Sa and Ss should windings oi'l Fig. 3

being vconnected to contacts oi' hand position as shown, making thesecondaryconnections for D. C. welding, -whereas in its right-handposition making secondary connections for A. C. welding.

For'D. C. welding thejapparatus has the position shown, and-the"transic'irmer l0' is confor three-phase ,operation. Primary windingSi ,and Ss are series-connected between .Y; windings S2' and -S4 areseries-'connected betweenthe terminals W `and isconnected betweentermimetered, the transformer is mutable for` opgratio'n on twodiii'erent supply voltages; the priwindings Si,

Si and Se being starsupply voltage. -and lbeng over from D. C. to A.'C.0p-

conditions. the

U acts-asa Underthese voltage in it.; left-lianaprimary side where meen4' in mien-nena' position, windings Si, 8o. and'i U andv, andvinilpreferably be provided with taps, as shown in'Figs. 3 and 4, inwhich the numerals placed near the indicate the voltage induced thereinwith a supply of voltage'of 380 volts.

The arrangement A. C. and D. C. welding with two different supplyvoltages is shown in Figs. 3, 4, 5, and 6, which also show twoadditional windings Sie and Sii. which are disposed on the core of thetransformer and .which serve to make the apparatus suitable for use on.two diierent supply voltages also in A. lC. welding.

In Figs. 3 and 4the D. C. welding; in Fig. connected for a high In Figs.5 and 6 the primary windings are arranged for A. C. welding; in Fig. 5the windings being arranged for the higher supply voltage, and in Fig.A6 for the lower supply voltage. In both Figs. 5' a.nd 6 the windings areconnected across a single phase of the'supply, and in Fig. `6 bothwindings Sio and S11 are in circuit.

.Instead of using change-over devices of the type devices may be used,i'or of switches 5 and 6, other instance. suitable plugs or terminals.It is, however, preferable Vthat the plugs be used on the intensity,vwhereas the terminals be used on the` secondary side. The weldingapparatus shown in Fig. 'Icomprises two. separate single-phasetransformers A and Bi however they may form, as in Figs,l l and 2, asingle transformer; preferably a leakage transformer whose primary andsecondary windings are separated from each other by adjustable magneticbridge pieces.. y The transformer A is proyided with a primary windingIl having its ends connected to terminals U and W', tw main secondarywindings Il and II; ltwo auxiliary secondary windings IG'and I1, and twoheating-current windings Il and I9.

nected to terminals Y windings 2l and 2l, s 22 and 2 3, and

the currents'have the lowest of the primary windings for I and V','tw`main secondary .f I two auxiliary secondary wind- In n. c. welding theprimary windings efirensformer A andB.are connected Iin the Scott' 'ar.rangement and for this purpose winding I I is pro-- vided with a'ntraltap )(,and theiratio between the ofwinding I2 andwinding'II connected toaterminal number of turns The winding I3 which is not used inl). C.welding, has a number ci turns equal to the diiIerence between thenumber of turns o! winding and ot winding |2.

For using the transformers with diierent supply voltages, winding isprovided with two taps -the transformer during A. C. welding, and `arenot \in use during D. C. welding. The windings lI5 and I1, and 22 and 23are located close to the primary windings and I2 respectively in orderthat a substantially constant voltage` will be induced therein. 4

The apparatus is provided with tour plug-type connectors Ki, Kn, Ks, andK4 adaptedrto receive U-shaped plugs 45and 4| connected to-the weldingcables. The connectors K1 and Ka are used for connecting the cables forD. C. welding and each consists of two connectingstrips 25 and 21,

.and 25and 25, whereas the connectors Ka and K4 are used ior A. C.welding and each consists of three terminal strips 35, 23|, and 35. Amore detailed description o! a suitable connector will be given inconnection with Fig. 9. The main secondary windings I4 and I5 areconnected in the following manner: The outer end' |55 of winding I4 isconnected to one oi the anodes ot tube I, and through the auxiliarywinding I5 to the strip 35, whereas the outer end I5| of winding |5 isconnected to the other anode of tube I, and throughthe auxiliary windingI1 to the strip 33.

Similarly the main secondary winding 25 has its outer end |52 connectedto one anode of tube 2, 'and through auxiliary winding 22 to the strip32, whereas winding 2| has its outer end |53 connected to the otheranode o! tube 2and through auxiliary winding 23 to the strip 35.

The inner ends |54 and |55 of windings |4 and 25 respectively, areconnected through a conductor |55 to the strips 25 and 3|, whereas theinner ends |51 and |55 o! windings i5 and 2| respectively, are connectedthrough a vconductor |55 to the strips 23| and 25.

' The heating-current windings I5 and I5 have their ends |55 and |5|connected to the ends of the cathode of tube fl, whereas their ends |52and |53 are connected throughconductors |54 and |55 respectively to thestrips 25 and 21, and also to the ends |55 and |51 oi' heating-currentwindings 24 and 25 whose free ends are connected to the cathode of tube2. Thus it is seen that when plug 45 is not inserted in the connectorKi. the voltages induced in windings I5 and |5 block the voltage inducedin windings 24 and 25, with the result that no heating current issupplied' to the cathodes of tubes I and 2. However, when the 'plug isinserted, windings |5 and i5 are placed in series across the cathode ortube I, whereas windings 24 and 25 are placed in series across thecathode of tube 2.

The necessary connections of the windings for A. C. and D. C. operationandfor two dinerent supply voltages is accomplished by means of thearrangement schematically shown in Fig. 8, in

which Li, La, and La are the terminals o! the 3- phase supply, 35 is aterminal block serving to make the connections for' .the uinerent supplyvoltages, and H is a switching device for connecting the windings for A.C. or D. C. welding.

The terminal block 35 is provided with a central row of four terminals|45, |4I, |42 and |43 and an upper and lower row o! four terminals each;the terminals of the upper and lower rows being marked with letterscorresponding to the terminals oi'v Fig. 1. For the higher supplyvoltages for instance 380 volts, the corresponding terminals of thecentral and upper rows are connected by means of suitable removableconnecting strips |44, whereas for the'lower supply voltage, forinstance 220 v., the strips |44 are changed over to connectv thecorresponding terminals of4 the central and lower rows. f

The switching device H comprises a rotary switch -having three L-shapedcontact arms 31, 35. and 35 insulated from each other and interlocked soas to rotate together, for instance by being xedly secured to a commonshaft. As indicated by the arrows, thearms have four positions; a D. C.position |15, anA. C. position I1I, and two neutral or inactivepositions |12 and |13. Each arm cooperates with four stationary contactsindicated by reference letters corresponding to the terminals of Fig. 7and to the supply terminals i.: and La.

- welding, the switching device H is in the position shown, and thenecessary connections are made between the windings whereby thesecondary windings o! Fig. '7 form a symmetrical four-phase system. Theplugs l4|i and 4| are connected` to the connectors Ki and K2respectively, whereby plug 45 connects strips 25 and 21 and plug 4|connects strips 25 and 25.

The connection of strips 25 and 21 causes the cathodes to be energizedin the manner described above.

On the other hand, when strips 25 and,25 are connected the neutral pointof the four-phase system is formed. More particularly. conductor |55 isconnected to conductor |55, thereby interconnecting the. ends |54, |51,|55. and |55 of windings I4. I5, 25 and 2| respectively.

When using vthe apparatus for A. C. welding, the switching device H isrotated into position I'II whereby the winding I3 is connected in serieswith the primary winding I2 as a result of which ot transformer B isequal to that of transformer A. Also the series connection of windingsI2 and I3 are placed in parallel with windings II, and this parallelarrangement connected across the terminals Lx and La; thus to asinglephase.

The plugs 45 and 4| are inserted in the connectors K: and ,K4respectiveiy,whereby the secondary windings are connected in parallel inthe following manner: windings I5 and I4 are connected in series betweenstrips 35 and 3|; windings I5 and II are connected in series betweenstrips 23| and 33; windings 25 and 22 are connected in series between'strips 32 and 3|; and windings 2| and 23 are connected in seriesbetween strips 23| and 5. Thus itis seen that plugs 45 and 4I in addi onto making the connection for the welding current, also act as switchingmembers both during the A. C. and D; C. welding.

A amiable construction ior tbe connectors Ki. Ka,Ksandxsisshownindetailinllg. 5. The connector shown corresponds totheconnector Ka and comprises a plate 55 of insulating material and threestrips 35. 23|, and 32 connected to the secondary windings by cables 4I,41 and-43 spectively. The strips 30 and 23| are supported from the plate5l by means of a bolt 52, and are insulated from each othergand from thebolt 52 by meansI of insulating members 42, 43, and 44. Passing' througha clearance hole near 'the end o`f plate 50 and through clearance holesinthe between strips 30 and strips 3|) and 23| is a bolt 49 to which issecured a ring 45 of conductive material. The strip 32 is mechanicallysecured and electrically connected to the bolt 49 and this iselectrically connected to the ring 45, whereas strips 30 and 23|arelinsulated from bolt 49 and from each other by means of insulatingbushings 53 and 54.

'I'he U-shaped plug 40 connected to a welding cable'is inserted into theconnector with one fork 23|, and the other between strip 23| and thering 45 connected to the strip 32. The connection can then berigidly'secured together with a. wing nut 5|.

The terminals Ki and K2 may be constructed, ,in a similar manner by fnection with specific examples and in specific applications, we do notwish to be limited thereto, but desire the vappended claims to beconstrued as broadly as permissible in view oi the prior, art.

What we claim is:l

1. A welding apparatus for supplying A. C. andv D. C. weldingcurrentfrom a polyphase alternating-current supply comprising, atransformer 'formed of a plurality of single-phase transformer portionshaving primary windings and secondary windings, at least one auxiliarywinding on\ said transformer, rectiiiers for changing into D. C. cur-.rent the current supplied by said secondary windings, and switchingmeans for changing the apparatus over to A. C. operation during whichthe welding-current'is taken directly fromthe secondary windings, saidmeansin its A. C. position connecting'thetransformer in'single phase andconnecting at least a portion of the primary windings ln parallel and atleast a portion of .the secondary windings in parallel; said means inits A. C. position also connecting said auxiliary winding in series withone of the other windings.

2. A welding apparatus'for supplying A. C. or D. C.- welding currentfrom a polyphase alternating-current supply comprising, a transformerhaving vtwo. cores, primary windings and secondary windings on each ofsaid cores, at least one auxiliary winding disposed on one of said Acores `near the primary windings, rectiiiers for wiainie changing intoD. C. welding current thev current supplied by said secondary windings.andswitching means for changing the apparatus over. to :A. C, operationduring which the welding current is taken directly from the secondarywindings. said means in its A. C. position connectingthe transformerinsingle phase and connecting at primary windings in parallel and at leasta portion of the secondary windings in parallel, said means in its A. C.podtion also connecting said auxiliary winding in series secondarywindings.

' A. C. operation during which the Vtion of the first, third,

the series connection of 3. A welding apparatus for supplying A. C. andjD. C. welding current from a polyphase alternating-current 4supplycomprising, a transformer formed oi' two single-phase transformerportions having primary windings and secondary windings arranged intheScott connection,=rectiiers'for changing into D. C. Welding current thecurrent supplied by said secondary windings, and switching meansforchanging the apparatus over to 4is taken directly from the secondarywindings, said means in its A. C. position connecting the transformer insingle-phase and connecting at ,least a portion of the primary windingsin parallel and at least a portion of the secondary windings inparallel.`

4. Awelding apparatus for supplying A. C. and D. C. welding current froma polyphase alternating-current supply comprising, a single-phasetransformer having two primary windings and a secondary winding, asecond single-phase transformer having three primary windings and asecondary winding, the number of turns of said primary windings havingthe ratioof 1i 1; 2 in accordance with the Scott connection, rectifersfor changing into D; C. current the current welding current supplied bysaid secondary windings, and switching means for changing the A. C.operation during which the welding current is supplied directly from thesecondary windings, said means in its A. C. position connecting said.primary windings in two cuits, one circuit comprising the seriesconnecand at leaslpart of the fourth winding, and the second circuitcomprising the second and at least part of vthe fth winding.

5. A welding apparatus for supplying A. C. and

D. C.'welding current from a polyphase alternating-current supplycomprising, ,a transformer formed oi' a plurality ofsingle-phase'transformer portions havingprlmary windings and secondarywindings, rectiers for changing into D; C. welding 'current the currentsupplied by said secondary windings, switching means including aplurality of connecting terminals and cooperating plugs for changing the-paratus over to A. C. operation during which the welding current issupplied directly from the secondary windings, said means in its A. C.position connecting at 'least a portion of the primary windings inparallel and at least a portionof the secondary windings in parallel,said terminals comprising '55 A apparatus over to parallel-connectedcir-A ing-current supply comprising, a transformez' formed of aplurality of single-phase transformer portions having primary windingsand secondary windings, reetiners for changing into D. C. weldingcurrent-the current supplied by said secondary windings, and yswitchingmeans including a plurality of connecting terminals and cooperatingplugs for changing the apparatus over to A. C. operation ,during which.the welding current is supplied directly from the secondary windings,said means in its A. C. position connecting atleastsomeofthcm'lmarywindingsinparallelandat least some of the secondarywindings in parallel, electrically connecting the strips" together andto each of said terminals comprising a plurality of the welding cableconnected thereto.

resilient strips of conductive material, means se- .HENDRIK ABRAHAMcuring said strips together, and means for insulat'- WIJNAND KHNKHAMER.5 ing said strips from each other, said strips being CLAMOR AUGUSTLAMBERTS.

connected to the ends oi' said secondary windings, NICOLAAS 'ANTHONY anda welding cable connected to each of said JOHANNES VOORHOEVE.

plugs, saidplugs when inserted into said terminals FRANS HENDRIK nuJONG.

